Abstract
Fairness is one of the basic requirements of E-Commerce protocols and applications. CEMBS is proved to be an important cryptographic building primitive in constructing fair exchange protocols. In this paper the drawbacks of existing CEMBS-implementing methods are analyzed. A new CEMBS-constructing method based on RSA signature is proposed, which is proved to be simple, efficient and secure. Afterwards, a fair exchange protocol is built using the newly constructed CEMBS. And the devised scheme in this paper is the first efficient CEMBS based on RSA signatures.